Question

Sum of the digits of a two digit number is 12 and the difference between the number operand by interchanging the two digit number is 18

Answer 1

Let the digit at unit place be x
and at tens place be 12-x
No. = 10(12-x)+x=120-10x+x=120-9x

On interchanging the digits
digit at unit place=12-x
digit at tens place=x
New no. formed=10x+(12-x)
... ... =10x+12-x
... ... =9x+12

ATQ
9x+12-(120-9x) = 18
9x+12-120+9x=18
18x=18-12+120
18x=126
x=126/18=7

Digit at unit place is 7
and at tens place is 12-7=5

so the no is 57.